As many as one in ten children have the poor reading and spelling skills that comprise developmental dyslexia. It is widely accepted that there is a neurological basis; however, the nature of that basis is hotly debated. Nevertheless, one consistent view is that poor phonological processing-the ability to access and manipulate the sound units of language-is involved in dyslexia. Indeed, a majority of children with reading deficits exhibit difficulties on an array of phonological processing tasks. A growing body of research has discovered that speech-sound transcription, as measured by electrophysiology, shows striking relationships with phonological processing skills and reading ability in school-age children. As such, we have developed a suite of subcortical and cortical physiological tests that probe some of the core deficits that researchers have postulated as the root elements of poor phonological processing. We will target the subcortical processing of time-varying signals and stimulus regularities, and cortical hemispheric specialization to both fast and slow signals. In a longitudinal cohort of four- to eight-year-olds, we will model the normal neurological speech transcription process, quantify its development, and examine its relationship with the development of literacy-related skills. Our intention is that by leveraging these electrophysiological probes to a pre-reading age group, a biomarker, in preschoolers, may be found that predicts a child's eventual reading skill as he/she progresses through the primary grades. If such a biomarker is found, it would pave the way for earlier and more effectively targeted intervention. PUBLIC HEALTH RELEVANCE: As objective neurophysiological measures of literacy become available, a logical step is to apply what has been learned about subcortical and cortical physiology and their relationships with reading to young pre- readers. The outcome of the proposed work will be a deeper understanding of the biological underpinnings of literacy, particularly in pre-literate children, and a means to exploit objective biological responses as biomarkers of future literacy. This outcome will positively impact our understanding of the core deficits leading to poor reading, and has the potential to spur early intervention programs to head off the potential onset of developmental dyslexia.